Sorted By Test Name - Mayo Medical Laboratories

PPFR
28116
PPFWE
31891
sensitivity to coagulation deficiencies. More sensitive thromboplastins have a low ISI (1.0-1.2), whereas
less sensitive thromboplastins have a higher ISI (eg, 2.0-3.0). Calculation of the INR is as follows: INR =
(Patient's PT/mean PT of reference range)ISI where: INR = International Normalized Ratio ISI =
International Sensitivity Index Recommended INR therapeutic ranges for orally administered drugs are as
follows: Anticoagulation Intensity INR Standard Intensity 2.0-3.0 Higher Intensity 3.0-4.5 The INR is
used only for patients on stable oral anticoagulant therapy. It makes no significant contribution to the
diagnosis or treatment of patients whose PT is prolonged for other reasons. At Mayo Clinic and for Mayo
Medical Laboratories' clients, the PT test is performed with a sensitive thromboplastin (ISI 1.0+/- 0.05),
containing phospholipid and recombinantly derived TF.
Useful For: Monitoring intensity of oral anticoagulant therapy when combined with INR reporting
Screening assay to detect deficiencies of 1 or more coagulation factors (factors I, II, V, VII, X) due to:
-Hereditary or acquired deficiency states -Vitamin K deficiency -Liver disease -Specific coagulation
factor inhibitors Screening assay to detect coagulation inhibition ("circulating anticoagulants") associated
with: -Specific coagulation factor inhibitors -Lupus-like anticoagulant inhibitors (antiphospholipid
antibodies) -Nonspecific PT inhibitors (eg, monoclonal immunoglobulins, elevated fibrin degradation
products)
Interpretation: The PT test varies in its sensitivity to the activity of coagulation factors II, V, VII, and
X, and is least sensitive to decreased factor II. According to Mayo Clinic Special Coagulation laboratory
validation, using recombinantly derived thromboplastin with ISI close to 1.0, the PT begins to become
prolonged when: Factor II